Cellulose has been modified in several ways. Cellulose acetates and acetate/butyrates have been well known for years and have found use as adhesives in packaging, as filters for blood, food, and water purification systems, and as components of synthetic fabrics such as rayon. These derivatives have a high degree of substitution (DS), i.e., DS=2 to 3, with 3 representing full acylation of non-terminal glucose units. Some commercially available cellulose acetates are approximately 50% or more by weight acetate. (See, for example, the description and specification for several commercially available products in Eastman's "Cellulose Esters", 1995, pp. 1-9 and 16.) The acetates are considered GRAS (Generally Recognized as Safe) materials and are approved for contact with food such as packaging materials (see Federal Register, 44, No. 38, 10751-10758, 1979). In subchronic oral toxicity studies in rats, administration of cellulose acetate at dosage levels of 0 to 5000 mg/kg, no adverse effects have been observed (Thomas, W.C., et al., Fd. Chem. Toxic., 1991, 29: 453-458).
Cellulose mixed esters have also been previously described. These derivatives, when acylated with a mixture of shorter acetyl and/or butyryl groups and longer groups, are typically prepared by the reaction of cellulose acetate and/or butyrate with fatty acid anhydrides or chlorides or direct reaction of cotton, which is 90% cellulose, or other cellulosic material with fatty acids. These derivatives have been disclosed as useful in film formation and textile treatment. See, for example, U.S. Pat. No. 1,990,483 to Graves, U.S. Pat. No. 2,400,494 to Fisher, and U.S. Pat. No. 2,611,767 to Allen and Hawkes.
Acylation of cellulose hydroxyl groups with higher fatty acids has also been reported. Cellulose was rendered more soluble in water by esterifying with two laurate (C.sub.12), palmitate (C.sub.16) or stearate (C.sub.18) groups per glucose unit (Gault, H., and Ehrmann, P., Compt. rend., 1923, 177: 124-127). The physical properties of cellulose triesters of homologous C.sub.2 to C.sub.18 fatty acids were published in 1935 by Sheppard and Newsome (J. Phys. Chem. 39:143-152). The research, however, did not then result in the marketing of a commercial product, but some of the findings relating to the acylation of cellulose were applied to the modification of cotton to provide dry and wet crease recovery, improved viscoelastic properties such as elongation at break, and the like (see, for example, U.S. Pat. No. 3,493,319 to Berni and McKelvey). Essentially fully substituted fatty acid cellulose esters have recently been suggested as potential biodegradable plastics (Kwatra, H.S., et al., Ind. Eng. Chem. Res., 1992, 31: 2647-2651). Most of the published syntheses of higher esters employed processes using reactants, solvents and/or catalysts not desirable for food use products, and, where the reaction products were characterized, they were highly substituted.
Various coatings and hydrolysis techniques have been disclosed as alternatives to the chemical substitution of cellulose to modify its properties for various uses, including incorporation into edible compositions. In U.S. Pat. No. 4,219,580 to Torres, for example, microcrystalline cellulose or an acid-treated starch derivative are processed with xanthan gum and a food grade emulsifier such as lecithin to provide a flour substitute. In the patent's examples, the coated product is employed in cake and cookie recipes. Similarly, Krawczyk, et al., suggested coprocessing particulate cellulose with a surfactant to form a composite that could be used as a bulking agent or functional formulary aid in chocolate confections (U.S. Pat. No. 5,505,982). Cellulose coatings that are physically sorbed, however, have a tendency to clump, and are difficult to disperse in some recipes. U.S. Pat. No. 5,445,678 to Whistler avoided this disadvantage by disclosing a granular starch that was partially hydrolyzed using acid or amylase and/or mechanically disintegrated to form a granular starch-derived microcrystalline starch composition, but it was so hydrolyzed that it was suggested for use as a fat substitute, not a flour substitute, in reduced calorie foods.
It would be desirable to have other methods of altering nondigestible cellulose. It would also be desirable to have other low calorie flour substitutes.